Improved method of producing a liquid tobacco extract

ABSTRACT

A method of producing a liquid tobacco extract is provided, the method including the steps of: preparing a tobacco material; heating the tobacco material at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius for at least 15 minutes, the tobacco material being heated directly; collecting volatile compounds released from the tobacco material during the heating step; and forming a liquid tobacco extract including the collected volatile compounds, the tobacco material being microwave heated during at least one step of the method. A liquid tobacco extract produced by the method is also provided.

The invention relates to a method of producing a liquid tobacco extract and to a liquid tobacco extract produced by such a method.

Aerosol-generating systems for delivering an aerosol to a user that comprise an atomiser configured to generate an inhalable aerosol from a liquid formulation, such as a liquid nicotine formulation, are known. Some known aerosol-generating systems comprise a thermal atomiser such as an electric heater that is configured to heat and vaporise the liquid formulation to generate an aerosol. One popular type of electrically heated aerosol-generating system is an e-cigarette. Other known aerosol-generating systems comprise a non-thermal atomiser that is configured to generate an aerosol from the liquid formulation using, for example, impinging jet, ultrasonic or vibrating mesh technologies.

Several methods for producing liquid tobacco extracts from tobacco material are known. Liquid tobacco extracts may be produced by a high temperature extraction process in which nicotine and other volatile flavour compounds are extracted from tobacco material and collected in a suitable solvent to form a natural liquid tobacco extract.

Maceration methods are also known, wherein a tobacco material is kept in suspension in an extraction liquid for a period of up to several weeks or even months. The resulting slurry is subsequently filtered, and the liquid phase thus collected can be used to manufacture a vaporisable liquid formulation. In one such method—so-called “cold maceration method”—there is generally no way of controlling the extraction conditions (e.g. temperature and pressure). In a variant of a maceration method, which has been described for example in US 2012/192880, the slurry is heated to 100 degrees Celsius or more.

The liquid phase collected upon filtration of the slurry, which represents the primary product of a maceration process, is highly diluted, and tends to have a low content of apolar tobacco flavour species. Additionally, the liquid phase typically contains little to no nicotine. As such, liquid extracts obtained by a maceration method generally need to be supplemented with additional ingredients, such as nicotine salts and glycerin, before being used in a vaporisable liquid formulation.

Alternative processes are known, wherein a tobacco material is substantially boiled in water for a period of hours or even days to form a vapour phase, and a distillate obtained by condensation of the vapour phase is continuously collected in a vessel. Over time, an oily, waxy layer containing a high proportion of apolar compounds builds up on the surface of the distillate.

On the one hand, the aqueous portion, above which the waxy layer builds up, and which contains nicotine and other water-soluble compounds, is recycled to the boiler. An apolar co-solvent may optionally be fed into the boiler with the aqueous portion in order to increase the extraction yield. On the other hand, the waxy phase is collected and ultimately forms the primary product of one such hydro-distillation process. Such product is often referred to as “tobacco essential oil”, and contains a high proportion of apolar compounds found in tobacco, such as fatty acids, neophytadiene, etc. The tobacco essential oil obtained by one such method typically contains no nicotine.

It is also known to subject tobacco material to an extraction process involving use of a volatile apolar solvent. Examples of suitable solvents are cyclic or acyclic short alkanes, as well as chlorinated solvents like dichloromethane. In one such process, the excess solvent may be evaporated by controlled heating under vacuum. Typically, this is done in the presence of ethanol, which has a higher boiling point than the extraction solvent, such that even traces of the extraction solvent can be detected.

The primary product of one such solvent-aided extraction process is often referred to as “tobacco absolute”, and may contain traces of ethanol. It is a waxy product and contains a highly concentrated mixture of most of the apolar compounds that can be extracted with the specific solvent, generally including nicotine, which is generally present at relatively high concentrations.

An alternative extraction process involves contacting a tobacco material with a solvent under supercritical conditions, such as supercritical carbon dioxide. One such process is disclosed in US 2013/160777, and relies on the principle that volatile substances within a feed material contacted with a supercritical fluid may partition into the supercritical phase. After dissolution of any soluble material, the supercritical fluid containing the dissolved substances can be removed, and the dissolved components of the feed matter can be separated out from the supercritical fluid. The primary product of a supercritical extraction process is substantially similar to the “tobacco absolute” of a solvent-aided extraction process run at lower temperature and pressure, contains no residual solvent and typically has a high level of the waxy, apolar compounds and includes nicotine, which is generally present at relatively high concentrations.

However, all the tobacco extracts obtainable by methods known in the art tend to have a very low level—if any—of compounds associated with the flavour of heated tobacco, such as furaneol.

In general, as discussed above, liquid tobacco extracts obtained by such known extraction processes may have a low level of nicotine. Further, liquid tobacco extracts obtained by such extraction processes may have a low level and low variety of flavour species. Liquid tobacco extracts obtained by such extraction processes may also have a high level of undesirable compounds. In general, the concentration of nicotine, flavour species and undesirable compounds obtained by such extraction processes may be significantly impacted by the type or types of tobacco used as a starting material.

A purpose of the invention is to alleviate one or more of the drawbacks of the liquid tobacco extracts obtained by known processes. In particular, it would be desirable to provide a method for the production of a novel and improved liquid tobacco extract. It would be particularly desirable to provide such a method for producing such a liquid tobacco extract that could be carried out more efficiently than existing processes.

The present disclosure relates to a method for producing a liquid tobacco extract from a tobacco material. The method may include the step of preparing a tobacco material. The tobacco material may be heated at an extraction temperature of between about 100 degree Celsius and about 160 degrees Celsius. The heating may be carried out for at least 15 minutes. The method may further comprise the step of collecting the volatile compounds released from the tobacco material during the heating step. The method may further comprise the step of forming a liquid tobacco extract comprising the collected volatile compounds. The tobacco material may be microwave heated during at least one step of the method.

According to the present invention there is provided a method of producing a liquid tobacco extract, the method comprising the steps of: preparing a tobacco material; heating the tobacco material at an extraction temperature of between about 100 degrees Celsius and about 160 degrees Celsius for at least about 15 minutes; collecting the volatile compounds released from the tobacco material during the heating step; and forming a liquid tobacco extract comprising the collected volatile compounds. According to the invention, the tobacco material is microwave heated during at least one step of the method.

According to the present invention there is further provided a liquid tobacco extract produced by the method of the present invention, as defined above.

As used herein with reference to the invention, the term “liquid tobacco extract” describes the direct product of an extraction process carried out on a tobacco material. Thus, the tobacco extract typically includes a mixture of natural components separated from, removed from, or derived from, a natural tobacco material using tobacco extraction processing conditions and techniques. Thus, in one such process extracted tobacco components are removed from the natural tobacco material and separated from unextracted tobacco components. According to the present invention, the extraction process for producing the liquid tobacco extract comprises heating the tobacco material under specific heating conditions and collecting the volatile compounds generated. The volatile compounds will be in gaseous form when released from the tobacco material. The liquid tobacco extract therefore consists of the mixture of natural tobacco components that have derived from the tobacco material and have been extracted or formed during the extraction process, typically in combination with one or more materials other than the tobacco material, such as a non-aqueous extraction solvent used during the extraction process. As will be described in more detail below, the volatile compounds released from the starting tobacco material may be collected using an absorption technique in which the volatile compounds are trapped in a non-aqueous extraction solvent. By way of example, an inert gas flow containing the volatile compounds may be directed into a container of a non-aqueous extraction solvent. The non-aqueous extraction solvent is preferably an aerosol former.

The present invention relates to a novel microwave assisted extraction method which includes a step of microwave heating the tobacco material at some stage during the extraction method. As described in more detail below, the tobacco material may be microwave heated prior to the heating step during which the tobacco material is heated to a temperature of between 100 degrees Celsius and 160 degrees Celsius, or the microwave heating may take place during the heating step.

The inclusion of a microwave heating step in the extraction method of the present invention has been found to significantly increase the nicotine extraction yield, in some cases by up to 600 percent compared to an equivalent extraction method without the microwave heating step. It is thought that this effect is due to the way in which the microwaves heat the tobacco from the inside, by rapidly heating the water molecules within the tobacco cells. When the water inside the tobacco cells boils, the volume inside the cell is expanded rapidly and the cell wall eventually ruptures. This increases the permeability of the plant material and importantly, releases components that are contained within the cell wall, such as nicotine. These components are then more available to be extracted during the heating step, such that the yield of these components is increased.

Microwave heating typically provides a higher penetration depth and more rapid heating of tobacco material than conventional resistive heating methods and this can advantageously result in a reduction in time required to carry out the extraction method. For example, the inclusion of the microwave heating step has been found by the inventors to result in a reduction of up to 80 percent in the duration of the heating step. Furthermore, a reduction in energy usage of up to 40 percent can be provided. Overall, the inclusion of the microwave heating step therefore enables the extraction process to be carried out very efficiently in terms of both energy and time.

Due to the way in which the microwaves heat the tobacco material from inside the tobacco cells, as described above, a more uniform heating of the tobacco material can also be achieved compared to conventional heating methods, such as resistance heating, which can only heat the tobacco material from the outside.

Microwave heating of the tobacco material can be carried out using relatively simple and low cost apparatus, which can be readily incorporated into existing extraction apparatus and methods.

In addition to the benefits provided by the microwave heating step, the extraction method of the present invention uses an extraction temperature within a specific range in combination with a specifically defined heating duration that advantageously provides an improved liquid tobacco extract having a significantly improved balance of desirable compounds to undesirable compounds. In particular, the extraction method of the present invention provides a liquid tobacco extract having a maximised ratio of desirable compounds to undesirable compounds for the tobacco material. For example, the use of the specific combination of extraction temperature and time as defined enables the levels of nicotine compounds to be optimised whilst also minimising the levels of undesirable compounds such as furans, carbonyls, phenols and TSNAs.

The inventors of the present invention have found that, in contrast to the existing extraction processes that have been discussed above, methods in accordance with the present invention advantageously provide a liquid tobacco extract that has a significantly higher content of compounds associated with the flavour of heated tobacco, such as for example furaneol. These compounds are substantially absent, or are present in trace amounts, in a tobacco extract obtained by a maceration process, which also typically contains little to no nicotine. These compounds are also generally absent or present in trace amounts in a tobacco extract obtained using a solvent, including under supercritical conditions. Similarly, a tobacco essential oil obtained by way of a distillation process also typically has a very low content—if any—of such compounds associated with the flavour of heated tobacco.

The liquid tobacco extracts obtained by methods in accordance with the invention present significant compositional differences with respect to tobacco extracts obtained by the existing extraction processes, and can be used as an e-liquid or for the preparation of an e-liquid that, when heated, generates an aerosol having a distinct composition and flavour characteristics compared with currently available e-liquids. In particular, liquid tobacco extracts obtained by a method in accordance with the invention may be used to generate an aerosol that provides a heated tobacco taste which more closely resembles an aerosol generated by conventional cigarettes or upon heating tobacco in a heat-not-burn device relative to available aerosols produced from existing liquid nicotine compositions.

The extraction method of the present invention enables a liquid tobacco extract to be produced which has optimised levels of nicotine and flavour compounds without the need for addition of such compounds after extraction. The resultant liquid tobacco extract can therefore advantageously be used directly to provide a nicotine composition. The resultant liquid tobacco extract can also be modified by one or more further processing steps or mixed with one or more further ingredients to form a nicotine composition. The nicotine composition can be for use in an e-cigarette or other aerosol-generating system.

Aerosol-generating systems for delivering an aerosol to a user that comprise an atomiser configured to generate an inhalable aerosol from a liquid formulation, such as a liquid nicotine composition, are known, as described above.

The method of producing a liquid tobacco extract of the present invention can be used effectively for all types and grades of tobacco, including Burley tobacco, flue-cured tobacco and Oriental tobacco. The method steps can be readily adjusted in order to provide a consistent liquid tobacco extract for a variety of blends of tobacco type. The extraction method is additionally suitable for a variety of forms of tobacco material.

In some cases, the tobacco material can be heated without the need for significant pre-treatment steps. The method can therefore be carried out efficiently.

During the method according to the present invention, the tobacco material is heated directly and is not suspended in a liquid solvent for the heating step, as in many types of prior art extraction processes. This provides greater control over the heating conditions of the tobacco material and also makes the extraction process more efficient. During heating, the volatile compounds are released from the tobacco material in gaseous form.

As defined above, in the method according to the present invention, the tobacco material is microwave heated at some stage during the extraction. The microwave heating is preferably carried out prior to, or during the heating step in order to optimise the effect of the microwave heating on the extraction yield.

In certain embodiments of the invention, the step of preparing the tobacco material comprises pre-treating the tobacco material by microwave heating to bring about rupture of the tobacco cells, prior to the heating step. In methods according to such embodiments, the microwave heating of the tobacco material is therefore carried out as a pre-treatment step prior to the main extraction. The microwave heating ruptures the cell walls of the tobacco material and releases the nicotine from within the tobacco cells, as described above, so that the nicotine is more available during the following heating step.

Preferably, during the pre-treatment step, the tobacco material is microwave heated to a temperature of between about 90 degrees Celsius and about 160 degrees Celsius, more preferably between about 95 degrees Celsius and about 110 degrees Celsius.

Preferably, during the pre-treatment step, the microwave heating is carried out for between about 1 minute and about 5 minutes.

Optionally, in methods according to the invention in which the tobacco material is pre-treated by microwave heating, the tobacco material is allowed to cool to ambient temperature (22 degrees Celsius) prior to the commencement of the heating step, in order to optimise the effectiveness of the main heating step. In some methods according to the invention there may be no cooling step between microwave pre-treatment and the heating step. This may improve efficiency of the process as the tobacco material may enter the main heating step at an elevated temperature.

Optionally, the tobacco material is microwave heated during the pre-treatment step in a flow of inert gas, such as nitrogen. This is believed to retain the humidity at a relatively low level such that the propagation of microwaves can be optimised. The positive impact of the microwaves on the extraction of nicotine and other compounds can therefore be maximised.

In embodiments in which the tobacco material is pre-treated by microwave heating prior to the main heating step, as described above, the step of heating the tobacco material to a temperature of between 100 degrees Celsius and 160 degrees Celsius may be carried out by conventional heating, for example, resistance heating or heating by steam. The conventional heating may be carried out, for example, in a conventional oven or dryer. In some embodiments, the tobacco material may be subjected to further microwave heating during the heating step, instead of conventional heating or in combination with conventional heating, as described in more detail below.

Alternatively or in addition to the inclusion of a pre-treatment step comprising microwave heating, the step of heating the tobacco material to a temperature of between 100 degrees Celsius and 160 degrees Celsius may comprise microwave heating the tobacco material. In such embodiments, the microwave heating of the tobacco material takes place during the main extraction step during which the volatile compounds are extracted in gaseous form from the tobacco material by heating. The microwave heating is therefore used to raise the temperature of the tobacco material to volatilise the tobacco compounds, as well as to rupture the tobacco cells to release the components from the tobacco cells, as described above.

In such embodiments, the step of heating the tobacco material to a temperature of between 100 degrees Celsius and 160 degrees Celsius may be carried out by microwave heating only.

Alternatively and preferably, the step of heating the tobacco material to a temperature of between 100 degrees Celsius and 160 degrees Celsius comprises a combination of microwave heating and conventional heating, such as resistance heating or heating by steam. In such methods, the microwave heating is used in addition to a conventional heating step and the tobacco material is heated simultaneously by microwaves and convention heating means, such as resistance heating means or steam. This combination of heating methods has been found to be particularly effective at increasing the extraction yield (in particular for nicotine), as the effect of the microwave heating appears to be optimised. Furthermore, by combining microwave heating with conventional heating in the main heating step, the heating step can advantageously be carried out significantly faster and with less energy. The efficiency of the extraction process is therefore optimised. In certain methods, it is useful to retain the conventional heating in combination with the microwave heating, rather than using microwave heating alone, as it may be easier to carry out certain heating steps with conventional heating means. For example, where the tobacco material is heated in a flow of inert gas, it may be necessary to heat the inert gas with resistance heating means.

Preferably, where a combination of heating methods is used, the microwave heating preferably provides between about 50 percent and about 90 percent of the heating power for heating the tobacco material to the desired extraction temperature.

The microwave heating of the tobacco material may be carried out using any suitable means for generating microwaves. An example of a suitable apparatus for microwave heating the tobacco material is the LABATRON™ ES3 integrated reactor and microwave transmission system from SAIREM, which can be used for carrying out microwave assisted extraction processes with a batch or continuous flow microwave reactor. This apparatus is suitable for embodiments in which the tobacco material is heated simultaneously by microwave and conventional heating, as described above.

The microwave power should be controlled to achieve the desired temperature of the tobacco material, depending upon the mass of tobacco material to be heated.

Preferably, the tobacco material is continuously circulated or agitated during the microwave heating. This could be achieved, for example, by heating the tobacco material inside a rotary dryer. The continuous circulation of the tobacco material avoids the formation of hot spots within the tobacco material, thereby improving the uniformity of the heating so that the extraction yields can be optimised.

Preferably, the water content of the tobacco material at the start of the microwave heating step is at least about 10 percent by weight, more preferably at least about 20 percent by weight. The water content of the tobacco material may be up to about 70 percent by weight at the start of the microwave heating step, more preferably up to about 50 percent by weight, more preferably up to about 40 percent by weight, more preferably up to about 30 percent by weight. For example, the water content of the tobacco material at the start of the microwave heating step may be between about 10 percent and about 70 percent by weight, or between about 10 percent and about 50 percent by weight, or between about 10 percent and about 40 percent by weight, or between about 10 percent and about 20 percent by weight.

It will be appreciated that “the water content in the tobacco material” may include both water inherently present in the tobacco material as well as any added water.

The presence of water in the tobacco material is important for optimising the effect of the microwave heating on the extraction, as it is the boiling of the water molecules inside the tobacco cells that will cause the rupture of the cells and the release of nicotine and other compounds. The water content of the tobacco material is therefore preferably retained at a level of at least 10 percent by weight. In particular, it is not desirable to dry the tobacco material prior to the microwave heating, as the cell rupture mechanism is found to be more effective when the tobacco material is not dried prior to microwave heating. The elimination of a drying step at this stage during the extraction method is advantageous, since it reduces the time and energy taken to prepare the tobacco material for the extraction, thereby further improving the overall efficiency of the method compared to prior art extraction methods.

In certain embodiments, methods according to the invention may further comprise a step of applying water to the tobacco material prior to the microwave heating step in order to increase the water content of the tobacco material, preferably to at least 10 percent by weight. For example, the tobacco material may be sprayed with liquid water, or contacted with steam to increase the water content prior to microwave heating.

In embodiments of the invention in which the tobacco material is pre-treated by microwave heating prior to the main heating step, as described above, the method according to the invention may further comprise the step of applying water to the tobacco material after the microwave heating step and prior to the main heating step in order to increase the water content of the tobacco material, preferably to at least 10 percent by weight. The microwave pre-treatment step is likely to reduce the water content of the tobacco material due to evaporation of the water from within the tobacco cell during heating. It is advantageous to restore the water lost from the tobacco material and bring the water content back up to at least 10 percent by weight in order to ensure that the subsequent heating step to extract the volatile compounds is optimised and any burning of the tobacco material is avoided.

Optionally, in methods according to the invention, water lost during a microwave pre-treatment step may be captured by subjecting off-gas produced during the pre-treatment step to a condensation process. This may advantageously also capture valuable volatile components of the tobacco which may also be lost during the pre-treatment step. The collected water and volatile components may then be used when remoisturising the pre-treated to tobacco. This may both remoisturise the tobacco and reduce potential losses of valuable volatile components.

As defined above, in the method of the present invention, the tobacco material is heated under specific heating conditions to release the volatile tobacco components, which are collected and formed into a liquid tobacco extract.

During the heating step, the tobacco material is heated to an extraction temperature of between about 100 degrees Celsius and about 160 degrees Celsius. It has been found that below this range, insufficient levels of nicotine and certain flavour compounds are released from the tobacco material such that the resultant liquid tobacco extract lacks the desired flavour characteristics. On the other hand, if the tobacco material is heated to a temperature above this defined range, unacceptably high levels of certain undesirable tobacco compounds may be released.

Preferably, the extraction temperature is at least about 110 degrees Celsius, more preferably at least about 115 degrees Celsius, more preferably at least about 120 degrees Celsius, more preferably at least about 125 degrees Celsius.

Preferably, the extraction temperature is no more than about 150 degrees Celsius, more preferably no more than about 145 degrees Celsius, more preferably no more than about 140 degrees Celsius, most preferably no more than about 135 degrees Celsius.

For example, the extraction temperature may be between about 110 degrees Celsius and 150 degrees Celsius, or between about 120 degrees Celsius and about 140 degrees Celsius, or between about 125 degrees Celsius and about 135 degrees Celsius, or about 130 degrees Celsius. An extraction temperature of around 130 degrees Celsius has been found to provide a particularly optimised ratio of desirable to undesirable compounds in the liquid tobacco extract.

The extraction temperature may be between about 110 degrees Celsius and about 130 degrees Celsius, or between about 115 degrees Celsius and about 125 degrees Celsius, or about 120 degrees Celsius.

The extraction temperature may be between about 125 degrees Celsius and about 155 degrees, more preferably between about 135 degrees Celsius and about 145 degrees Celsius, or about 140 degrees Celsius.

The tobacco material is heated at the extraction temperature for at least about 15 minutes, preferably for at least about 20 minutes, more preferably for at least about 25 minutes, more preferably for at least about 30 minutes, more preferably for at least about 40 minutes, more preferably for at least about 50 minutes, more preferably for at least about 60 minutes. This extraction time is sufficiently long that the desired tobacco flavour compounds can be extracted efficiently to provide a liquid tobacco extract that can produce an aerosol having the desired flavour characteristics. As described above, the inclusion of a microwave heating step in the extraction method of the present invention enables the heating step to be carried out relatively quickly, with a significantly shorter heating duration than is typically required in prior art extraction processes.

Preferably, the tobacco material is heated at the extraction temperature for no more than about 180 minutes, more preferably no more than about 120 minutes.

For example, the heating time may be between about 15 minutes and about 180 minutes, or between about 15 minutes and about 120 minutes, or between about 20 minutes and about 180 minutes, or between about 20 minutes and about 120 minutes, or between about 25 minutes and about 180 minutes, or between about 25 minutes and about 120 minutes, or between about minutes and about 180 minutes, or between about 30 minutes and about 120 minutes, or between about 40 minutes and about 180 minutes, or between about 40 minutes and about 120 minutes, or between about 50 minutes and about 180 minutes, or between about 50 minutes and about 120 minutes, or between about 60 minutes and about 180 minutes, or between about 60 minutes and about 120 minutes.

The heating time indicated above corresponds to the duration of time over which the tobacco material is heated at the extraction temperature and does not include the time taken to increase the temperature of the tobacco material up to the extraction temperature.

The extraction temperature and the duration of heating may be selected within the ranges defined above depending upon factors such as the type of tobacco, possible other components of the tobacco material, the desired level of nicotine or the desired composition of the liquid tobacco extract. By controlling the combination of extraction temperature and time, the composition of the liquid tobacco extract can be adjusted depending on the desired characteristics of the aerosol generated from the liquid tobacco extract. In particular, the proportion of specific tobacco compounds within the liquid tobacco extract can be adjusted to a certain degree through the selection of the extraction parameters in order to maximise the ratio of desirable to undesirable tobacco compounds within the liquid tobacco extract.

For a specific tobacco compound, the variation in the level of release of the compound with extraction temperature during the extraction process can be readily determined for any given tobacco material. For example, it has been found that the level of nicotine released from a tobacco material will typically increase with increasing extraction temperature. The rate of increase has been found to vary for different tobacco types.

It has also been found that the level of desirable tobacco flavour compounds, such as β-damascenone and β-ionone, released from a tobacco material will increase with increasing extraction temperature up to a certain peak extraction temperature, after which the level will begin to decrease. The peak extraction temperature for such flavour compounds is typically within the range of 100 degrees Celsius to 160 degrees Celsius such that the level of desirable flavour compounds can be effectively optimised in the extraction method of the present invention.

Many undesirable tobacco compounds have been found to increase slowly with increasing extraction temperature up to a threshold temperature, beyond which a rapid increase is observed. This applies, for example, to the level of phenolic compounds, TSNAs and pyrazines and in the case of Bright tobaccos, to the level of furans and formaldehyde. In many cases, the threshold temperature is within the range of 100 degrees Celsius to 160 degrees Celsius and therefore the level of the undesirable compounds can be effectively controlled in the extraction method of the present invention.

Preferably, the extraction temperature and extraction time are selected to provide a nicotine content in the liquid tobacco extract of at least 0.1 percent by weight, more preferably at least about 0.2 percent by weight.

Preferably, the extraction temperature or the extraction time or both the extraction temperature and the extraction time are selected to provide a ratio by weight of (β-ionone+β-damascenone) to (phenol) of at least about 0.25 in the liquid tobacco extract.

β-damascenone and β-ionone are desirable compounds associated with tobacco flavour. It has been found that the amount of β-damascenone and β-ionone released from a tobacco material will increase with increasing the extraction temperature up to a certain peak extraction temperature, after which the level will begin to decrease. The peak extraction temperature for such flavour compounds is typically within the range of 100 degrees Celsius to 160 degrees Celsius such that the level of desirable flavour compounds can be effectively tailored and controlled in the extraction method.

Preferably, the extraction temperature or the extraction time or both the extraction temperature and the extraction time are selected to provide a ratio by weight of (furaneol+(2,3-diethyl-5-methylpyrazine)*100)) to (nicotine) of at least about 5×10⁻⁴ in the liquid tobacco extract.

As discussed above, the heating step may be carried out by conventional heating, microwave heating, or a combination of conventional heating and microwave heating.

Suitable heating methods for carrying out the conventional heating of the tobacco material would be known to the skilled person and include but are not limited to: dry distillation, hydrodistillation, vacuum distillation, flash distillation and thin film hydrodistillation.

The heating step is preferably carried out in an inert atmosphere. Preferably, a flow of an inert gas, such as nitrogen, is passed through the tobacco material during the heating step. In some cases, a flow of a combination of an inert gas with water or steam may be used. The addition of water or steam to the tobacco during extraction has been found to increase yield of extracted components. However, excess addition of water or steam leads to processing difficulties such as stickiness of the tobacco material.

The volatile tobacco compounds are released into the flow of inert gas during the heating step such that the inert gas (or combination of inert gas with water or steam) acts as a carrier for the volatile components. The inert gas flow rate may be optimised based on the scale and geometry of the extraction chamber. A relatively high flow rate of inert gas may advantageously improve the efficiency of extraction from the tobacco material.

In general, upon heating the tobacco material, any moisture present in the tobacco material is also released with the volatile compounds, in the form of steam.

The flow of inert gas helps convey the steam generated by evaporation of the moisture content of the tobacco material and the volatile compounds—including, in particular, nicotine or flavour-associated compounds or both—out of the extraction equipment. Furthermore, in methods where the tobacco material is heated by microwave heating during this step, the flow of inert gas has been found to advantageously retain the humidity within the extraction chamber at a relatively low level so that propagation of the microwaves through the tobacco material is maximised.

Further, use of a flow of inert gas, such as nitrogen, under light over-pressure in the extraction equipment has the benefit of preventing the presence of oxygen within the extraction equipment. This is desirable in that it prevents risk of any, even partial, combustion of the tobacco material during the heating step. Uncontrolled combustion of the tobacco material would clearly be undesirable as it would represent a major safety risk within the manufacturing environment. However, the inventors have found that even a limited, partial combustion of the tobacco material may lead to a decrease in the quality of the tobacco extract obtainable by the method, which would be undesirable.

Without wishing to be bound by theory, it is understood that, by preventing combustion of the tobacco material, the formation of any undesirable combustion by-products is also prevented. Further, as conditions that would be conducive to combustion of the tobacco material are prevented, the tobacco material is effectively heated under conditions that mimic, to an extent, conditions under which a tobacco-containing substrate (e.g. homogenised tobacco material) is typically heated in “heat-not-burn” articles. As a result, selective extraction of the flavour-bearing volatile species responsible for the taste consumers associate with heated tobacco is advantageously favoured.

Therefore, by carrying out the heating step in an inert atmosphere, the extraction efficiency, product quality and manufacturing safety are advantageously enhanced.

The heating of the tobacco material in a flow of inert gas has the additional benefit that the inert gas flow containing the volatile compounds may be more easily directed into a container containing an extraction solvent, such as a non-aqueous extraction liquid solvent.

Optionally, the heating step may be carried out under vacuum. This removes any oxygen present within the extraction chamber, which may advantageously prevent reaction of the tobacco material or volatile compounds generated upon heating of the tobacco material with oxygen. The removal of oxygen will also prevent any combustion of the tobacco material, as described above.

Methods according to the present invention may further comprise the step of spraying atomised water into the extraction chamber during the heating step. This has been found to improve heat exchange during the heating step, which is thought to be due to the turbulent flow that is set up within the extraction chamber as a result of the evaporation of the atomised water. As a result of the improved heat exchange, the inclusion of the step of spraying water into the extraction chamber during the heating step has been found to provide a further improvement in the nicotine yield, as well as an increase in the yield of certain desirable flavour compounds from the tobacco material. Where the heating step comprises microwave heating, as described above, the presence of water also optimises the effect of the microwaves on the tobacco material.

The spray of atomised water may be generated and dispensed into the extraction chamber using any suitable means.

The flow rate at which the atomised water is sprayed into the extraction chamber may be adjusted, for example, depending upon the flow rate of the tobacco material within the extraction chamber. For example, the average flow rate at which the atomised water is sprayed into the extraction chamber may be between about 3 percent and about 30 percent of the flow rate of the tobacco material.

Preferably, the atomised water is sprayed at a pressure of at least about 1 bar, more preferably at least about 2 bar, more preferably at least about 3 bar.

Methods of atomising water would be known to the skilled person. In some embodiments, the water may be atomised in a flow of compressed inert gas, such as air. In other embodiments, the water may be atomised without a flow of gas, due to the pressure within the spray nozzle.

The liquid tobacco extract may be produced from a tobacco material consisting of a single type of natural tobacco. Alternatively, the tobacco material may comprise a blend of two or more types of natural tobaccos. The ratio of the different tobacco types may be adapted depending on the desired characteristics of the aerosol generated from the liquid tobacco extract. For example, where it is desired to provide a relatively high level of nicotine, the proportion of Burley tobacco may be increased.

The term “natural tobacco” is used herein with reference to the present invention to describe any part of any plant member of the genus Nicotiana, including, but not limited to, leaves, midribs, stems and stalks. In particular, the natural tobacco may comprise flue-cured tobacco material, Burley tobacco material, Oriental tobacco material, Maryland tobacco material, dark tobacco material, dark-fired tobacco material, Rustica tobacco material, as well as material from other rare or specialty tobaccos, or blends thereof. As will be described in more detail below, the tobacco material may be whole (for example, whole tobacco leaves), shredded, cut or ground.

Where it is desired to produce a liquid tobacco extract from a combination of two of more different tobacco types, the tobacco types may be heated separately at different extraction temperatures within the defined range of 100 degrees Celsius to 160 degrees Celsius, or a mixture of the tobacco types may be heated together at a single extraction temperature within the range.

The tobacco material may be a solid tobacco material, such as a powder, leaf scraps or shreds, or intact leaf. Alternatively, the tobacco material may be a liquid tobacco material such as a dough, gel, slurry, or suspension.

The tobacco material may be derived from any suitable tobacco material, including but not limited to tobacco leaf, tobacco stem, reconstituted tobacco, cast tobacco, extruded tobacco or tobacco derived pellets.

Preferably, in the step of preparing the tobacco material, the tobacco is ground or cut in order to reduce the size of tobacco particles within the tobacco material. This may advantageously improve the homogeneity of heating of the tobacco material and the efficiency of the extraction.

The tobacco material may optionally be dried prior to the heating step in order to decrease the water content of the tobacco material. Drying of the tobacco material may be carried out by any suitable chemical or physical drying process. Alternatively and preferably, water may be added to the tobacco material prior to the heating step in order to increase the water content of the tobacco material, in particular where microwave heating is used during this stage.

In certain embodiments of the present invention, the step of preparing the tobacco material may comprise the step of impregnating the tobacco material with an aerosol former. When this impregnation of the tobacco material is carried out prior to the heating step, it may advantageously increase the amount of certain desirable tobacco compounds that are released from the tobacco material upon heating. For example, impregnation of the tobacco material with glycerin has been found to advantageously increase the amount of nicotine that is extracted from the tobacco material. In another example, impregnation of the tobacco material with a non-aqueous extraction solvent that is also an aerosol former, such as propylene glycol, vegetal glycerin, 1,3-propanediol, triacetin, or mixtures thereof has been found to advantageously increase the amount of flavour compounds that are extracted from the tobacco material.

In some embodiments, the tobacco material consists of natural tobacco that has not been subjected to any pre-treatment steps, for example, to adjust the water content. As such, a water content in the tobacco material may be about 10 to 20 percent by weight (water content typically found in natural tobacco material). In other embodiments, the tobacco material may comprise added water, as described above.

Alternatively or in addition, the tobacco material may comprise one or more additional ingredients, such as for example a non-aqueous solvent. An example of a suitable solvent is propylene glycol.

The tobacco material may thus comprise at least about 40 percent by weight of natural tobacco material or at least about 60 percent by weight of natural tobacco material or at least about 80 percent by weight of natural tobacco material or at least about 90 percent by weight of natural tobacco material or at least about 95 percent by weight of natural tobacco material.

In some embodiment, the non-aqueous solvent content may be at least about 5 percent by weight or at least about 10 percent by weight or at least about 15 percent by weight or at least about 20 percent by weight or at least about 25 percent by weight or at least about 30 percent by weight or at least about 35 percent by weight or at least about 40 percent by weight.

Optionally, the tobacco material may be digested enzymatically prior to the heating step. This has been found to provide a significant increase in the yield of certain flavour compounds from the tobacco material.

In certain embodiments, in the step of preparing the tobacco material, the tobacco is not subjected to any treatment adapted to alter the pH of the tobacco. In particular, in the step of preparing the tobacco material, the tobacco is not subjected to any treatment adapted to significantly increase the pH of the tobacco.

In other embodiments, the method further comprises the step of subjecting the tobacco material to an alkali treatment prior to the heating step. Where the method comprises a pre-treatment step of microwave heating the tobacco material, the alkali treatment is preferably carried out prior to the microwave heating. During the alkali treatment, an alkaline solution is preferably applied to the tobacco material to provide alkalised tobacco material and the alkalised tobacco material is then used for the extraction.

The inclusion of an alkali treatment step prior to the heating of the tobacco material has been found to provide a further significant increase in the yield of nicotine that is obtained during the extraction.

Preferably, the pH of the alkalised tobacco material is at least about 8.5, more preferably at least about 9.0, more preferably at least about 9.5. Preferably, the pH of the alkalised tobacco material is no more than 11.

The “pH of the alkalised tobacco material” refers to the pH of an aqueous suspension of the alkalised tobacco material which is formed by making a suspension of the alkalised tobacco material in water at a ratio of 1:20. The pH of the suspension is measured after 30 minutes soaking time.

As described above, in the alkaline treatment step, an alkaline solution is applied to the tobacco material prior to heating. A suitable alkaline solution may be selected, for example, depending on the desired pH of the tobacco material. Preferably, the alkaline solution is an aqueous solution of an alkali agent. A preferred example of a suitable alkaline solution for the alkaline treatment step is an aqueous solution of potassium carbonate. Other suitable alkaline solutions for use in the present invention include but are not limited to sodium hydroxide, sodium carbonate and hydrogen peroxide.

The tobacco material may optionally be analysed prior to the heating step in order to determine the composition, for example, the content of reducing sugars of alkaloids. This information about the composition may helpfully be used to select an appropriate extraction temperature.

During the heating of the tobacco material, the volatile compounds are released in gaseous form from the tobacco material. The volatile compounds are collected using any suitable technique. Where the tobacco material is heated in a flow of an inert gas, as described above, the volatile compounds are collected from the inert gas flow. Different collection methods would be well known to the skilled person.

In certain preferred embodiments, the step of collecting the volatile compounds uses an absorption technique in which the volatile compounds are trapped in a non-aqueous extraction liquid solvent. For example, an inert gas flow containing the volatile compounds may be directed into a container of a non-aqueous extraction liquid solvent. The non-aqueous extraction liquid solvent is preferably an aerosol former such as triacetin, glycerin, 1,3-propanediol, propylene glycol or combinations thereof. The use of an aerosol former as the liquid solvent is potentially beneficial because the aerosol former can be retained as a diluting agent in the final liquid tobacco extract. This means that an additional step of removing the non-aqueous extraction solvent is not necessarily required.

As used herein with reference to the present invention, the term “aerosol former” refers to a compound or mixture of compounds that, in use, facilitates formation of an aerosol, and that preferably is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article or device. Examples of suitable aerosol-formers include: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1,3-propanediol, and glycerin; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

Preferably, the non-aqueous liquid solvent is retained at a temperature of less than 0 degrees Celsius in order to optimise the transfer of the volatile compounds into the liquid solvent. The non-aqueous extraction solvent is preferably retained at a temperature of no less than −10 degrees Celsius. Temperatures below such value may lead to undesirable freezing phenomena.

In alternative preferred embodiments, the step of collecting the volatile compounds may be carried out using a condensation technique in which the volatile compounds are condensed and the condensate is collected. Condensation of the volatile compounds may be carried out using any suitable apparatus, for example, in a refrigerated column. Preferably, the condensate obtained is added to a liquid aerosol former, preferably propylene glycol.

The addition of a liquid aerosol former in the collection step, and particularly addition of propylene glycol, may advantageously prevent the condensed volatile compounds from splitting into two phases or forming an emulsion, as some tobacco constituents would tend to do. Without wishing to be bound by theory, the inventors have observed that the solubility of the tobacco constituents in the hydrolate (i.e. the aqueous fraction of the liquid, naturally derived tobacco extract) depends primarily on their polarity, on their concentration and on the pH of the hydrolate, which may vary depending on the tobacco type. As a result, an oily layer tends to form at the surface of the liquid, naturally derived tobacco extract, if the amount of aerosol former is not sufficient. Such oily material can aggregate at different locations on the trapping and desiccation equipment wherein the third and further steps of the method are carried out, respectively. The addition of a liquid aerosol former, such as propylene glycol, helps prevent the formation of such layer and favours homogenisation of the liquid, naturally derived tobacco extract. This, in turn, helps prevent any loss of desirable flavour-associated compounds during the fourth (desiccation) step, during which such compounds may undesirably deposit on the equipment surfaces.

In addition, the liquid aerosol former advantageously helps trap the flavour-associated compounds independent of their polarity and volatility. Further, during any subsequent drying step, the liquid aerosol former helps prevent loss of the most volatile fraction, as well as favour the selective removal of excess water from the liquid, naturally derived tobacco extract to obtain the concentrated tobacco extract.

Use of propylene glycol as the aerosol former for the collection step has the further advantage that, by reducing the water activity of aqueous solutions, propylene glycol exerts an anti-microbial activity. By adjusting the content of propylene glycol in the liquid tobacco extract, it is therefore also possible to ensure that the extract substantially does not undergo any microbial activity.

As a further alternative, the step of collecting the volatile compounds may be carried out using an adsorption technique in which the volatile compounds are adsorbed onto the surface of a solid adsorbent material, such as activated carbon. The adsorbed compounds are then transferred into a liquid solvent.

In the method of the present invention, the next step is the formation of a liquid tobacco extract from the collected volatile compounds. The nature of this step may depend upon the collection method. The “collected volatile compounds” will typically comprise a solution of the tobacco derived volatile compounds in a liquid solvent or carrier.

Where the volatile compounds are collected by absorption in a non-aqueous extraction solvent, as described above, the extraction method provides a liquid tobacco extract that may comprise greater than about 25 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract may comprise greater than about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract or greater than about 35 percent by weight of non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

The liquid tobacco extract may comprise less than or equal to about 65 percent of non-aqueous extraction solvent based on the weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract may comprise less than or equal to 60 percent of non-aqueous extraction solvent based on the weight of the liquid tobacco extract or less than or equal to 55 percent of non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

In some embodiments, the liquid tobacco extract may comprise from about 25 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 25 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 25 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

In other embodiments, the liquid tobacco extract may comprise from about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

In further embodiments, the liquid tobacco extract may comprise from about 35 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 35 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 35 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The non-aqueous extraction solvent is preferably triacetin, glycerin, propylene glycol, 1,3-propanediol or a mixture thereof.

In preferred embodiments, in the liquid tobacco extract a ratio by weight of (β-ionone +β-damascenone) to (phenol) is at least about 0.25.

In preferred embodiments, in the liquid tobacco extract a ratio by weight of (furaneol+(2,3-diethyl-5-methylpyrazine)*100)) to (nicotine) is at least about 5×10⁻⁴.

Where the volatile compounds are collected by absorption in a liquid solvent, as described above, the step of forming the liquid tobacco extract preferably comprises drying the solution of the volatile compounds in the liquid solvent in order to concentrate the solution. This may be carried out, for example, in order to arrive at a desired concentration of nicotine, or flavour compounds. Drying may be carried out using any suitable means, including but not limited to desiccation, molecular sieves, freeze drying, phase separation, distillation, membrane permeation, controlled crystallisation of water and filtering, reverse hygroscopicity, ultracentrifugation, liquid chromatography, reverse osmosis or chemical drying.

In preferred embodiments, the solution of the volatile compounds in a liquid solvent is concentrated by desiccation.

In other words, the solution of the volatile compounds in a liquid solvent is heated to evaporate at least some of the water and obtain a concentrated tobacco extract. To this purpose, the solution of the volatile compounds in a liquid solvent may be heated to a temperature and for a time such that the water content in the tobacco extract is reduced by at least about 60 percent.

The partially desiccated, concentrated tobacco extract can be considered the primary product of a method in accordance with the present invention. Depleted tobacco material, from which the volatile species and most of the moisture content have been extracted upon heating during the second step, may be considered a by-product of the method. Such depleted tobacco material may typically have a moisture content of about 1 to 5 percent by weight, preferably about 2 to 3 percent by weight.

In an embodiment, the solution of the volatile compounds in a liquid solvent is heated under vacuum, preferably at a temperature of at least about 70 degrees Celsius. In another embodiment, the solution of the volatile compounds in a liquid solvent is heated under a flow of air, preferably under a flow of air having relatively low humidity, at a temperature of at least about 35 degrees Celsius. Thus, a naturally derived, concentrated tobacco extract can be obtained by a method in accordance with the invention. One such naturally derived, concentrated tobacco extract typically contains less than about 20 percent by weight of water.

Alternatively, where the volatile compounds are collected by condensation, the step of forming the liquid tobacco extract may comprise adding the condensate to a liquid solvent, such as an aerosol former.

Optionally, the step of forming the liquid tobacco extract comprises a filtering step.

Optionally, the step of forming the liquid tobacco extract comprises a blending step in which extracts derived from different tobacco materials are combined.

Optionally, the step of forming the liquid tobacco extract comprises adding one or more additives, such as an organic acid, to the solution of volatile compounds. However, in many cases the liquid tobacco extract is suitable for use without the inclusion of additives.

The present invention further provides a liquid tobacco extract produced by a method according to the first aspect of the invention, as described in detail above. As described above, the method of the present invention advantageously produces a natural liquid tobacco extract that has a highly desirable ratio of desired tobacco compounds, such as nicotine and flavour compounds, to undesirable tobacco compounds.

The liquid tobacco extract is particularly suitable for producing a nicotine composition, such as a liquid nicotine composition or a gel nicotine composition, for use in an aerosol-generating system. In such an aerosol-generating system, the nicotine composition is typically heated within an aerosol-generating device.

As used herein, the term “aerosol-generating device” refers to a device comprising a heater element that interacts with a nicotine composition incorporating a liquid tobacco extract such as that obtained by a method in accordance with the invention to produce an aerosol. During use, volatile compounds are released from the nicotine composition by heat transfer and entrained in air drawn through the aerosol generating device. As the released compounds cool they condense to form an aerosol that is inhaled by the consumer.

Upon heating of a nicotine composition comprising the liquid tobacco extract according to the present invention, an aerosol is released containing the volatile compounds that have been collected from the tobacco material during the extraction process. By controlling the composition of the liquid tobacco extract through control of the parameters of the extraction parameter, it is possible to adjust the composition and characteristics of the resultant aerosol produced from the liquid tobacco extract and delivered to the consumer.

The nicotine composition may be a liquid tobacco extract resulting from an extraction process in accordance with the present invention, without the addition of further nicotine. The nicotine composition may be a liquid tobacco extract resulting from an extraction process in accordance with the present invention, without the addition of further flavour compounds. The nicotine composition may be a liquid tobacco extract resulting from an extraction process in accordance with the present invention, without the addition of further furaneol. The nicotine composition may be a liquid tobacco extract resulting from an extraction process in accordance with the present invention, without the addition of further solvent.

Alternatively, the liquid tobacco extract may be subjected to additional processing steps to form the nicotine composition. Even when subjected to such additional steps, the nicotine composition may be formed without the need for addition of further nicotine or flavour compounds.

Preferably, the liquid tobacco extract may be concentrated in a desiccation step as described above to form a concentrated tobacco extract, and the concentrated tobacco extract may be used to form the nicotine composition.

Preferably, the concentrated tobacco extract comprises between 8 percent and 15 percent by weight water based on the weight of the concentrated tobacco extract.

The desiccation step provides a concentrated tobacco extract that may have a non-aqueous extraction solvent content of from about 65 percent to about 95 percent by weight, preferably from about 65 percent to 85 percent by weight, most preferably from about 75 percent to about 85 percent by weight. The non-aqueous extraction solvent is preferably triacetin, glycerin, propylene glycol, 1,3-propanediol or a mixture thereof.

The desiccation step provides a concentrated tobacco extract that may have a nicotine content of at least about 0.2 percent by weight nicotine, preferably from about 0.5 percent by weight to about 12 percent by weight nicotine, most preferably from about 2 percent by weight to about 8 percent by weight nicotine.

Preferably, additional non-aqueous solvent may be added to the liquid tobacco extract or the concentrated tobacco extract to form the nicotine composition.

The nicotine composition may be a liquid nicotine composition or a gel nicotine composition.

The nicotine composition may comprise at least about 10 percent by weight of a liquid tobacco extract. Preferably, the nicotine composition comprises at least about 20 percent by weight of a liquid tobacco extract. More preferably, the nicotine composition comprises at least about 30 percent by weight of a liquid tobacco extract. In preferred embodiments, the nicotine composition comprises at least about 40 percent by weight of a liquid tobacco extract, more preferably at least about 50 percent by weight of a liquid tobacco extract, even more preferably at least about 60 percent by weight of a liquid tobacco extract. In particularly preferred embodiments, the nicotine composition comprises at least about 65 percent by weight of a liquid tobacco extract, more preferably at least about 70 percent by weight of a liquid tobacco extract, even more preferably at least about 75 percent by weight of a liquid tobacco extract, most preferably at least about 80 percent by weight of a liquid tobacco extract.

In some embodiments, the liquid tobacco extract is concentrated tobacco extract. The nicotine composition may comprise at least about 10 percent by weight of concentrated tobacco extract, at least about 20 percent by weight of concentrated tobacco extract, at least about 30 percent by weight of concentrated tobacco extract, at least about 40 percent by weight of concentrated tobacco extract, at least about 50 percent by weight of concentrated tobacco extract, preferably at least about 60 percent by weight of concentrated tobacco extract, more preferably at least about 70 percent by weight of concentrated tobacco extract, even more preferably at least about 75 percent by weight of concentrated tobacco extract, and most preferably at least about 80 percent by weight of concentrated tobacco extract.

In some embodiments, the nicotine composition comprises from about 40 percent by weight to about 95 percent by weight of a liquid tobacco extract. More preferably, the nicotine composition comprises from about 40 percent by weight to about 95 percent by weight of a liquid tobacco extract. Even more preferably, the nicotine composition comprises from about 50 percent by weight to about 95 percent by weight of a liquid tobacco extract. Most preferably, the nicotine composition comprises from about 60 percent by weight to about 95 percent by weight of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises from about 70 percent by weight to about 95 percent by weight of a liquid tobacco extract, even more preferably from about 80 percent by weight to about 95 percent by weight of a liquid tobacco extract.

In some embodiments, the nicotine composition comprises from about 40 percent by weight to about 90 percent by weight of a liquid tobacco extract. More preferably, the nicotine composition comprises from about 40 percent by weight to about 90 percent by weight of a liquid tobacco extract. Even more preferably, the nicotine composition comprises from about 50 percent by weight to about 90 percent by weight of a liquid tobacco extract. Most preferably, the nicotine composition comprises from about 60 percent by weight to about 90 percent by weight of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises from about 70 percent by weight to about 90 percent by weight of a liquid tobacco extract, even more preferably from about 80 percent by weight to about 90 percent by weight of a liquid tobacco extract.

In some embodiments, the nicotine composition comprises from about 40 percent by weight to about 85 percent by weight of a liquid tobacco extract. More preferably, the nicotine composition comprises from about 40 percent by weight to about 85 percent by weight of a liquid tobacco extract. Even more preferably, the nicotine composition comprises from about 85 percent by weight to about 90 percent by weight of a liquid tobacco extract. Most preferably, the nicotine composition comprises from about 60 percent by weight to about 85 percent by weight of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises from about 70 percent by weight to about 85 percent by weight of a liquid tobacco extract, even more preferably from about 80 percent by weight to about 85 percent by weight of a liquid tobacco extract.

The nicotine composition may comprise up to about 100 percent by weight of a liquid tobacco extract. In some embodiments, the nicotine composition may be formed directly from the liquid tobacco extract without the need for addition of additional non-aqueous solvent, flavourants or nicotine. That is to say, the nicotine composition may comprise 100 percent by weight of a liquid tobacco extract. In some embodiments, the liquid tobacco extract is concentrated tobacco extract, such that the nicotine composition may comprise 100 percent by weight of concentrated tobacco extract. In embodiments in which the nicotine composition comprises 100 percent by weight of a liquid tobacco extract or 100 percent by weight of concentrated tobacco extract, additional non-aqueous solvent is not present.

Alternatively, in some embodiments, the nicotine composition comprising liquid tobacco extract may comprise additional non-aqueous solvent. Additional non-aqueous solvent is non-aqueous solvent that has been added after the extraction step. Additional non-aqueous solvent is solvent that is supplemental to the non-aqueous extraction solvent present in the liquid tobacco extract. In embodiments in which the liquid tobacco extract is concentrated tobacco extract, the nicotine composition comprising concentrated tobacco extract may comprise additional non-aqueous solvent.

The additional non-aqueous solvent may be an aerosol former. Preferably, the additional non-aqueous solvent is triacetin, glycerin, propylene glycol, 1,3-propanediol or a mixture thereof.

In embodiments in which the nicotine composition comprises additional non-aqueous solvent, the nicotine composition may comprise 90 percent by weight or less of the additional non-aqueous solvent. Preferably, the nicotine composition comprises 80 percent by weight or less of the additional non-aqueous solvent. More preferably, the nicotine composition comprises 70 percent by weight or less of the additional non-aqueous solvent. In preferred embodiments, the nicotine composition comprises about 60 percent by weight or less of the additional non-aqueous solvent, more preferably about 50 percent by weight or less of the additional non-aqueous solvent, even more preferably about 40 percent by weight or less of the additional non-aqueous solvent.

In particularly preferred embodiments, the nicotine composition comprises about 35 percent by weight or less of the additional non-aqueous solvent, more preferably about 30 percent by weight or less of the additional non-aqueous solvent, even more preferably about 25 percent by weight or less of the additional non-aqueous solvent, most preferably about 20 percent by weight or less of the liquid tobacco extract.

In a nicotine composition prepared by means of a method in accordance with the present invention at least 50 percent by weight based on the total weight of the nicotine composition of the nicotine content in the nicotine composition may come from the tobacco extract as opposed to being added following extraction. In preferred embodiments, at least 80 percent by weight based on the total weight of the nicotine composition of the nicotine content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction. Even more preferably, at least 90 percent by weight based on the total weight of the nicotine composition of the nicotine content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.

In a nicotine composition prepared by means of a method in accordance with the present invention at least 50 percent by weight based on the total weight of the nicotine composition of the non-aqueous extraction solvent content in the nicotine composition may come from the tobacco extract as opposed to being added following extraction. In preferred embodiments, at least 80 percent by weight based on the total weight of the nicotine composition of the non-aqueous extraction solvent content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction. Even more preferably, at least 90 percent by weight based on the total weight of the nicotine composition of the non-aqueous extraction solvent content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.

In a nicotine composition prepared by means of a method in accordance with the present invention at least 50 percent by weight based on the total weight of the nicotine composition of the water content in the nicotine composition may come from the tobacco extract as opposed to being added following extraction. In preferred embodiments, at least 80 percent by weight based on the total weight of the nicotine composition of the water content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction. Even more preferably, at least 90 percent by weight based on the total weight of the nicotine composition of the water content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.

In a nicotine composition prepared by means of a method in accordance with the present invention at least 50 percent by weight based on the total weight of the nicotine composition of the desirable tobacco flavour species content in the nicotine composition may come from the tobacco extract as opposed to being added following extraction. In preferred embodiments, at least 80 percent by weight based on the total weight of the nicotine composition of the desirable tobacco flavour species content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction. Even more preferably, at least 90 percent by weight based on the total weight of the nicotine composition of the desirable tobacco flavour species content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.

The total content of non-aqueous solvent in the nicotine composition includes the non-aqueous extraction solvent and the additional non-aqueous solvent, if it is present. The nicotine composition may comprise a total content of non-aqueous solvent of from about 10 percent to about 95 percent by weight. The nicotine composition preferably comprises a total content of non-aqueous solvent of from about 50 percent to about 95 percent by weight, for example from about 65 percent to about 95 percent by weight, more preferably from about 70 to about 90 percent by weight, most preferably from about 80 percent to about 90 percent by weight. The non-aqueous solvent is preferably triacetin, glycerine, propylene glycol, 1,3-propanediol or a mixture thereof.

The nicotine composition may comprise a total content of propylene glycol of from about 10 percent to about 95 percent by weight. The nicotine composition may comprise a total content of propylene glycol of from about 20 percent to about 95 percent by weight, such as from about 50 percent to about 95 percent by weight, or from about 65 percent to about 95 percent by weight, from about 70 to about 90 percent by weight, or from about 80 percent to about 90 percent by weight.

The nicotine composition may comprise a total content of triacetin of from about 10 percent to about 95 percent by weight. The nicotine composition may comprise a total content of triacetin of from about 20 percent to about 95 percent by weight, such as from about 50 percent to about percent by weight, from about 70 to about 90 percent by weight or from about 65 percent to about 95 percent by weight, or from about 80 percent to about 90 percent by weight.

The nicotine composition may comprise a total content of glycerine of from about 10 percent to about 95 percent by weight. The nicotine composition may comprise a total content of glycerine of from about 20 percent to about 95 percent by weight, such as from about 50 percent to about percent by weight, or from about 65 percent to about 95 percent by weight, from about 70 to about 90 percent by weight or from about 80 percent to about 90 percent by weight.

The nicotine composition may comprise a total content of 1,3-propanediol of from about 10 percent to about 95 percent by weight. The nicotine composition may comprise a total content of 1,3-propanediol of from about 20 percent to about 95 percent by weight, such as from about 50 percent to about 95 percent by weight, or from about 65 percent to about 95 percent by weight, or from about 80 percent to about 90 percent by weight.

The nicotine composition of the present invention comprises at least 0.2 percent by weight of nicotine. More preferably, the nicotine content in the nicotine composition liquid tobacco extract is at least about 0.4 percent by weight. The nicotine composition may have a nicotine content of about 12 percent by weight or less, for example about 10 percent by weight or less, preferably about 8 percent by weight by weight or less, more preferably about 5 percent by weight or less, preferably about 3.6 percent by weight or less. Most preferably, the nicotine composition comprises between about 0.4 percent by weight and 3.6 percent by weight nicotine, based on the weight of the nicotine composition.

The nicotine composition may comprise between 1 percent and 85 percent by weight of water. The nicotine composition may comprise between 2 percent and 50 percent by weight of water. The nicotine composition may comprise between 3 percent and 30 percent by weight of water. The nicotine composition may comprise between 5 percent and 25 percent by weight of water. The nicotine composition may comprise between 8 percent and 20 percent by weight of water. The nicotine composition preferably comprises between 10 percent and 15 percent by weight water.

In some embodiments, the nicotine composition may comprise one or more water-soluble organic acids. As used herein with reference to the invention, the term “water-soluble organic acid” describes an organic acid having a water solubility at 20° C. of greater than or equal to about 500 mg/ml.

The one or more water-soluble organic acids may advantageously bind nicotine in the liquid tobacco extract through formation of one or nicotine salts. The one or more nicotine salts may advantageously be dissolved and stabilised in the water present in the liquid tobacco extract or in the non-aqueous solvent. This may advantageously reduce nicotine adsorption in the upper airways and enhance pulmonary nicotine delivery and retention as discussed above.

Preferably, the nicotine composition has a water-soluble organic acid content of greater than or equal to about 2 percent by weight. More preferably, the nicotine composition has a water-soluble organic acid content of greater than or equal to about 3 percent by weight.

The water-soluble organic acid may be acetic acid.

Exogenous acetic acid is acetic acid that has been added from a source other than the tobacco plant material, and is not acetic acid that is naturally present in the tobacco plant that has been separated from, removed from or derived from the tobacco plant material using the extraction processing conditions and techniques.

If acetic acid is added to the liquid tobacco extract to form the nicotine composition, then the total content of acetic acid in the nicotine composition, including both exogenous and endogenous acetic acid, is preferably from about 0.01 percent to about 8 percent by weight, for example between about 0.03 percent to about 8 percent by weight, from about 0.3 percent to about 8 percent by weight, from about 2 percent to about 8 percent by weight, or from about 3 percent to about 8 percent by weight. More preferably, the total acetic acid content is from about percent to about 6 percent by weight, for example between about 0.03 percent to about 6 percent by weight, from about 0.3 percent to about 6 percent by weight, from about from about 2 percent to about 6 percent by weight, or from about 3 percent to about 6 percent by weight.

Preferably, the nicotine composition has a water-soluble organic acid content of less than or equal to about 8 percent by weight. More preferably, the nicotine composition has a water-soluble organic acid content of less than or equal to about 6 percent by weight.

Preferably, the nicotine composition has a water-soluble organic acid content of between about 2 percent by weight and about 8 percent by weight. For example, the nicotine composition may have a water-soluble organic acid content of between about 2 percent by weight and about 6 percent by weight.

More preferably, the nicotine composition has a water-soluble organic acid content of between about 3 percent by weight and about 8 percent by weight. For example, the nicotine composition may have a water-soluble organic acid content of between about 3 percent by weight and about 6 percent by weight.

The nicotine composition may comprise one or more non-tobacco-derived flavourants. Suitable non-tobacco-derived flavourants include, but are not limited to, menthol.

Preferably, the nicotine composition has a non-tobacco-derived flavourant content of less than or equal to about 4 percent by weight. More preferably, the nicotine composition has a non-tobacco-derived flavourant content of less than or equal to about 3 percent by weight. For example, the liquid tobacco extract produced by the method of the present invention may be used to make a nicotine composition comprising between 10 and 20 mg of nicotine per millilitre, without the need for addition of nicotine.

A nicotine composition suitable for use in an aerosol-generating system may comprise the liquid tobacco extract produced in a method according to the present invention in combination with water and additional aerosol former. The nicotine composition may comprise, for example, between about 10 percent by weight and about 20 percent by weight of water.

A nicotine composition comprising the liquid tobacco extract according to the present invention may be provided in a cartridge for use in an aerosol-generating system. The cartridge may comprise an atomiser, configured to generate an aerosol from the nicotine composition. The atomiser may be a thermal atomiser, which is configured to heat the nicotine composition to generate an aerosol. The thermal atomiser may comprise, for example, a heater and a liquid transport element configured to transport the nicotine composition to the heater. The liquid transport element may comprise a capillary wick. Alternatively, the atomiser may be a non-thermal atomiser, which is configured to generate an aerosol from the nicotine composition by means other than heating. The non-thermal atomiser may be, for example, an impinging jet atomiser, an ultrasonic atomiser or a vibrating mesh atomiser.

The cartridge containing the nicotine composition formed from the liquid tobacco extract of the present invention may be used in conjunction with any suitable aerosol-generating device comprising a housing configured to receive at least a portion of the cartridge. The aerosol-generating device may comprise a battery and control electronics.

Specific embodiments of the present invention will now be further described, by way of example only.

In an extraction method according to a first embodiment, a tobacco material is prepared from a flue-cured Bright tobacco material. The tobacco material is cut to form tobacco shreds having maximum dimensions of 2.5 millimetres by 2.5 millimetres and the tobacco shreds are pre-treated by microwave heating until the tobacco cells are caused to rupture. The pre-treated tobacco shreds are cooled and then placed in a humidity chamber to increase the water content to about 10 percent by weight. The tobacco shreds are then fed into an extraction chamber, without compression, at a tobacco flow rate of 30 kg per hour. The tobacco material is heated within the extraction chamber to a temperature of 130 degrees Celsius for a period of 2 hours. During heating, a flow of nitrogen is passed through the extraction chamber at a flow rate of about litres per minute.

The volatile compounds released from the tobacco material during the heating step are collected by condensation at 0 degrees Celsius and added to a liquid solvent formed of propylene glycol.

The solution of propylene glycol with the collected volatile compounds is concentrated in a desiccation process to reduce the moisture level of the liquid tobacco extract to approximately percent.

In an extraction method according to a second embodiment, a tobacco material is prepared from a flue-cured Bright tobacco material. The tobacco material is cut to form tobacco shreds having dimensions of 2.5 millimetres by 2.5 millimetres and water is applied to the tobacco material to increase the water content to about 20 percent by weight. The tobacco shreds are loaded into an extraction chamber, without compression. The tobacco material is heated within the extraction chamber to a temperature of 130 degrees Celsius for a period of 30 minutes. The heating is carried out by a combination of microwave heating and resistance heating, with the microwave heating providing at least 50 percent of the power to heat the tobacco material. During heating, a flow of nitrogen is passed through the extraction chamber at a flow rate of about 40 litres per minute.

The volatile compounds released from the tobacco material during the heating step are collected by condensation at 0 degrees Celsius and added to a liquid solvent formed of propylene glycol. The solution of propylene glycol with the collected volatile compounds is concentrated in a desiccation process to reduce the moisture level of the liquid tobacco extract to approximately percent. 

1.-15. (canceled)
 16. A method of producing a liquid tobacco extract, the method comprising the steps of: preparing a tobacco material; heating the tobacco material at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius for at least 15 minutes, wherein the tobacco material is heated directly; collecting volatile compounds released from the tobacco material during the heating step; and forming a liquid tobacco extract comprising the collected volatile compounds, wherein the tobacco material is microwave heated during at least one step of the method.
 17. The method according to claim 16, wherein the step of preparing the tobacco material comprises pre-treating the tobacco material by microwave heating to bring about rupture of tobacco cells, prior to the heating step.
 18. The method according to claim 17, wherein the step of heating the tobacco material is carried out by conventional heating.
 19. The method according to claim 16, wherein the step of heating the tobacco material comprises microwave heating the tobacco material.
 20. The method according to claim 19, wherein the step of heating the tobacco material comprises heating the tobacco material by a combination of microwave heating and conventional heating.
 21. The method according to claim 17, wherein the tobacco material is heated in a flow of inert gas during at least one of the heating step and the pre-treating step.
 22. The method according to claim 16, wherein the tobacco material has a moisture content of at least 10 percent by weight at a start of the microwave heating.
 23. The method according to claim 16, further comprising the step of applying water to the tobacco material prior to the microwave heating step in order to increase a moisture content of the tobacco material to at least 10 percent by weight.
 24. The method according to claim 16, wherein the tobacco material is continuously circulated during the microwave heating.
 25. The method according to claim 16, wherein the tobacco material is heated at an extraction temperature of between 125 degrees Celsius and 160 degrees Celsius.
 26. The method according to claim 16, wherein the extraction temperature is selected to provide a liquid tobacco extract having a nicotine content of at least 0.2 percent by weight based on dry weight.
 27. The method according to claim 17, further comprising the step of subjecting the tobacco material to an alkali treatment prior to the heating step and prior to the pre-treating step.
 28. The method according to claim 16, further comprising the step of spraying atomised water onto the tobacco material during the heating step.
 29. The method according to claim 16, further comprising the step of drying or concentrating the collected volatile compounds.
 30. A liquid tobacco extract produced by the method of claim
 16. 